1997 Oldsmobile Achieva Code Reading

My check Engine Light came on today and I had the Code Read and it stated Oxygen Sensor on Bank one was running to Lean. That Oxygen sensor is the one next to the Catalitic Converter. My question is do you think the Oxygen sensor it self is at Fault or would it be dumping to much unburned gas out the Exhaust. A week Before the Check Engine light came on the car started a small hestitation when you first went to take off from a light or stop sign but would be fine once you started going. Any Suggestions or help on this. That was the only code it read by the way. Thanx in advance